1. Field of the Invention
The present invention relates to a sealing device for sealing between a shaft hole housing and a member such as a shaft or the like at an inner peripheral side thereof by a seal lip, in a motor vehicle, a general machine, an industrial machine or the like, and more particularly to a structure having an oil injection port for injecting oil for lubricating a slide portion of the seal lip.
2. Description of the Conventional Art
As a typical prior art of a sealing device for sealing fluid by a seal lip on an outer periphery of a rotating shaft, for example, structures disclosed Japanese Unexamined Patent Publication No. 2005-188668 and Japanese Unexamined Patent Publication No. 10-169785 are well known.
FIG. 7 is a half sectional view showing a conventional sealing device by cutting along a plane passing through an axis. In this FIG. 7, reference numeral 100 denotes a sealing device (an oil seal). The sealing device 100 is provided with a reinforcing ring 103 having an approximately L-shaped cross section, an attaching portion 101 integrally formed by a rubber-like elastic material on an outer peripheral tube portion of the reinforcing ring 103, and a seal lip 102 integrally formed by a rubber-like elastic material on an inner peripheral portion of the reinforcing ring 103 so as to be directed to an inside space A. The attaching portion 101 is pressure inserted and fixed to an inner peripheral surface of a shaft hole housing 200, and the seal lip 102 is slidably brought into close contact with an outer peripheral surface of a rotating shaft 300, whereby the sealing device seals the inside space A.
In this kind of sealing device, in order to lubricate a sliding portion S between the seal lip 102 and the rotating shaft 300, there is a sealing device structured such as to inject oil O to the sealing device 100 from an oil injection port 201 provided in the shaft hole housing 200. Further, in this case, if the oil O is directly injected toward the sliding portion S, the seal lip 102 is lifted up from an outer peripheral surface of the rotating shaft 300 on the basis of an injecting pressure, and there is a risk that a leakage is caused. Accordingly, the oil O is injected toward a waist portion 104 at an outer peripheral side from the seal lip 102, as illustrated.
However, in this case, if the oil O injected at a pressure about 0.2 MPa from the oil injection port 201 rebounds from the waist portion 104 of the sealing device 100 and hits against the outer peripheral surface of the seal lip 102 strongly, there is a risk of generation of local abrasion of the seal lip 102 caused by a local surface pressure increase of the sliding portion S, and a leakage caused by non-uniformity of surface pressure distribution with respect to a circumferential direction, because a tolerable pressure limit of the sealing device 100 is about 0.03 MPa.
Further, as a countermeasure thereof, there can be considered to improve the tolerable pressure limit (a rigidity) by increasing a thickness of the seal lip 102, however, in this case, it is unavoidable that a tracking performance of the seal lip 102 is deteriorated with respect to an eccentricity of the rotating shaft 300, and a sliding load is increased by an increase of press force applied to the rotating shaft 300. As a result, there is a risk of deterioration of a rubber material caused by an increase of sliding heat generation, an increase of a friction torque, early abrasion of the seal lip 102 and the like.